Conventionally, a sheet feed unit for use in an image forming apparatus includes a sheet feed unit body and a sheet cassette, which is withdrawable from the sheet feed unit body.
The sheet cassette stores a plurality of recording medium such as transfer sheet used for image forming, and the recording medium (e.g., transfer sheet) is fed from the sheet cassette to an image forming section one by one.
As for such sheet feed unit, an operator conducts sheet-refilling or sheet-replacement by withdrawing the sheet cassette from the sheet feed unit body.
In case of the sheet-refilling, the operator refill recording medium (e.g., transfer sheet), and in case of the sheet-replacement, the operator changes the size of the recording medium (e.g., transfer sheet) from one size to another size (e.g., from A4 to A3).
In general, an image forming apparatus includes a sheet feed unit having a locking mechanism to hold a sheet cassette at a predetermined position in the sheet feed unit body, from such position the recording medium (e.g., transfer sheet) is fed for image forming.
Such locking mechanism operation includes one of the steps of: (1) holding by a locking pawl and a spring; (2) holding by a Y-shaped catch mechanism having a pivotable arm, shaft, roller, spring, and frame; (3) holding by a Y-shaped catch mechanism made of resin material, and (4) holding by a leaf spring having a locking shape using elasticity of the leaf spring, for example.
Furthermore, the position of the sheet cassette in the sheet feed unit body is held by another mechanism such as a link mechanism for a sheet-feed position and a sheet-size detection switch provided on the sheet feed unit body, wherein the link mechanism for the sheet-feed position links the sheet cassette and the sheet feed unit body to set sheets to a sheet-feedable position when the sheet cassette is set in the sheet feed unit body, and the sheet-size detection switch detects a sheet size with contacting a sheet selection device provided in the sheet cassette.
Such sheet cassette is slidably configured to the sheet feed unit body, and is withdrawable from the sheet feed unit body, in general.
With such configuration, when an operator withdraws the sheet cassette from the sheet feed unit body for sheet-refilling or sheet-replacement, the operator needs to exert a force to detach the sheet cassette from the sheet feed unit body at the above-mentioned locking mechanism, to exert another force to detach the sheet cassette from the link mechanism for sheet-feed position and sheet-size detection switch, and to exert yet another force to overcome a sliding resistance of sliding portion of the sheet feed unit, for example.
Accordingly, the operator needs to exert a relatively large combined force to withdraw the sheet cassette from the sheet feed unit due to the above-mentioned forces.
Under such configuration, when the operator pushes the sheet cassette into the sheet feed unit body to set the sheet cassette to the sheet-feedable position, the operator receives reactive forces from the locking mechanism, the link mechanism, and the sheet-size detection switch, and sliding resistance at the sliding portion of the sheet feed unit, for example.
Thereby the operator also needs to exert a relatively large force when inserting the sheet cassette into the sheet feed unit body.
With the advent of the barrier-free trend and universal design, manufactures have been requested to produce machines or tools having improved accessibility for people including disabilities. For example, the Rehabilitation Act of the United States requires federal agencies to make their electronic and information technology accessible to people with disabilities.
Under such circumstances, it is desirable to manufacture an image forming apparatus having improved accessibility for people including disabilities. For example, it is preferable that the operator can insert the sheet cassette into the sheet feed body and withdraw the sheet cassette from the sheet feed body with less operating force.